Q: We have a 6-year-old pyracantha. The problem is we had no berries the first three years, then it did great for a year, the next two years the berries were brown, and this year we had no flowers or berries. Any idea what the problem might be?

A: Pyracantha â€“ often called â€œfirethornâ€ for its bright red berries and long-needled stems that are weapons-grade sharp â€“ can be gorgeous or extremely frustrating. They flower and fruit on year-old wood, so one thing that goes wrong is shearing the whole thing heavily every fall or spring. That encourages a lot of new growth, but since the fruits donâ€™t form on first-year growth, youâ€™ll end up with nothing but leaves. You canâ€™t cut them way back after flowering either, or youâ€™ll remove the baby berries that wouldâ€™ve matured into those beautiful red clusters in fall.

The best way to prune is selectively â€“ by thinning out excess branches back to a main stem and then pruning the rest lightly so there is a decent amount of year-old wood left to flower and fruit. You can also selectively prune as flowering is winding down. That way you can see which branches will have fruits and which are barren.

Other reasons why pyracantha might not fruit: 1.) young age or recent transplant (which might explain your non-fruiting the first three years); 2.) not enough sunlight, and 3.) lack of phosphorus or potassium in the soil. Pyracantha do not need a male and female to produce fruit like hollies, so thatâ€™s not an issue here.

That brings us to a fourth and most likely possibility: disease. Pyracantha are prone to a fungal disease called scab, and thatâ€™s what I think your plant has. This fungus causes dark spots on the leaves and olive-green spots on the fruits that evolve into shriveled-up wrinkly brown dots. In bad enough cases, scab can weaken the plant enough to abort fruiting and kill branches.

One good thing you can do is rake up diseased, fallen leaves and remove dead and infected branches. To prevent future outbreaks, you also may end up having to spray with a fungicide every 10 days from the time the new leaf buds begin to open until two weeks after the flower petals drop (or until the weather gets hot and dry). Chemical fungicides labeled for pyracantha scab include chlorothalonil, mancozeb and thiophanate-methyl. Neem oil and sulfur are natural alternatives that may help.

For those thinking about planting pyracantha, head off scab by choosing a disease-resistant variety, such as â€˜Apache,â€™ â€˜Mohaveâ€™ or â€˜Navaho.â€™